Triangle mesh based 3D surface characterisation for additive manufacturing parts inspection

Additive manufacturing (AM) produces components with intricate geometries, such as complex shapes, lattice structures, and 3D surface topography featuring re-entrant features and undercuts. X-ray computed tomography (XCT) is a valuable tool for measuring unique characteristics of AM surfaces, including particle features, surface cracks, and open porosity. Understanding the impact of these features is essential for predicting the performance of AM parts in fatigue, heat exchange, and osseointegration applications. However, characterising these XCT-measured features presents significant challenges. Firstly, their complex base or reference surfaces cannot be adequately described using Euclidean-space-based methods. Secondly, the surfaces measured are typically represented by polygon meshes rather than the lattice grid data used by conventional surface measurement instruments. As a result, standard surface characterisation techniques based on regular lattice grids, such as profile/areal surface parameters, form removal through fitting, filtration (Gaussian, spline, and robust filtration), and feature characterisation, are not directly applicable to these surfaces. This paper introduces the triangle mesh-based 3D surface characterisation method developed by CPT in collaboration with Digital Surf. The method encompasses a general characterisation framework, 3D surface parameters, freeform mesh fitting, and the latest advancements in triangle mesh-based filtration for separating the reference mesh and SL surface to analyse surface parameters.